1. Field of the Invention
The present invention relates to a segmented or laminated pipe-bending die.
2. Description of the Related Art
Pipe bending of the type described herein is required for large diameter pipe used in pipeline construction. Typically, machines for bending pipe having a diameter of 6xe2x80x3 or greater use the pipe-bending die of the present invention. Machines for bending the pipe may be of the types shown in Toderick U.S. Pat. No. 3,009,507 or Heaman U.S. Pat. No. 5,123,272. Toderick discloses a tractor-mounted side-boom. Heaman shows a self-propelled press. Other machines known as vertical pipe bending machines are also known for bending pipe on-site in pipeline construction.
All the pipe bending machines require at least one shoe or die which contacts the pipe to be bent to establish the configuration of the desired degree of pipe bend. Once the shoe or die is in place, other portions of the pipe are forced in opposition to the force exerted on the pipe by the die.
Pipe bending and metal working dies of the prior art are disclosed in the following United States Patents.
Toderick, U.S. Pat. No. 3,009,507 discloses a segmented pipe-bending shoe. Each segment is mounted on a common spring 64.
Amano, et al., U.S. Pat. No. 4,089,198 disclose a metalworking die having a retractable portion 17 formed of a number of links to adjust the working length of portion 17.
Green, U.S. Pat. No. 4,362,044 shows a pipe-bending die where pipe contact with the die is on surfaces 20, 25.
Heaman, U.S. Pat. No. 5,123,272 discloses a pipe-bending machine where the dies are divided into a number of transverse segments, which are moveable to distribute the load among all the segments. Each segment may have hydraulic support. A flexible membrane may cover the segments.
Codatto, U.S. Pat. No. 5,642,639 shows a segmented holder, which varies the thickness of each segment.
De Rossi, et al, U.S. Pat. No. 5,775,156 describe an equation for selecting the width of the segments of a sheet bending die.
Walczak U.S. Pat. No. 5,878,619 teaches a punch and die assembly for sheet metal processing. The die is formed of a number of plates.
Sarkisian, et al, U.S. Pat. No. 5,950,481 describe a segmented die for use in a forging press. Each of the segments has a different shape and is advanced along with movemeht of a work piece so that a relative large work piece can be shaped on a relatively small press.
Another prior art die is constructed by forging steel in a mold to produce a one-piece die with a surface of the required shape.
The present invention provides a pipe-bending die formed from a plurality of metallic segments, which are affixed together. Each metallic segment of the die has a semi-circular pipe contacting surface portion. The radius of the semi-circular pipe-contacting surface of each segment differs in length so that the pipe-contacting surface has a predetermined curvature formed by the resultant difference in height of the pipe contacting surface portions of each segment. In addition, each segment may be made so that the bottom surfaces of the segmented die adjacent the opening of the semi-circular pipe contacting surface are formed with the same degree of curvature as that formed in the pipe contacting surface. The segmented construction of the die has demonstrated simplicity, as it has no moving parts. Such a segmented construction also has proven to be easier to construct and therefore less costly, than the die formed by molten steel poured into a mold.
The segmented die of the present invention is used in the vertical pipe bending machines offered by a number of suppliers namely Darby Equipment Company, Evans Pipeline Construction Company, and DMI Industrial, Inc., and CRC Pipeline Equipment all of Tulsa Okla.
Such vertical pipe bending machines are generally illustrated in FIGS. 1-2 of the present application. These machines operate by moving a section of pipe into the machine and positioning it under the die and the point where the bend is to commence. A hydraulic cylinder called a pin-up cylinder forces a wedge under a shoe known as a pin-up shoe to raise it to engage the pipe. Another hydraulic cylinder is connected to the stifiback pipe supporting shoe to pull the stiffback up pushing the pipe against the die. With the die acting as the fulcrum, this hydraulic cylinder pushes the end of the stiffback shoe up, bending the pipe. After each bending operation, the pipe is moved through the machine an increment and the operation repeated until the desired angle of bend is achieved. The pipe is always moved toward the pin-up shoe when bending, thus keeping a straight portion of the pipe in the stiffback shoe during bending. Each size of pipe required a different size bending die. Each size of pipe, smaller than the maximum the machine will handle, requires a set of liners in addition to the die. The liners fit into the stiffback shoe and the pin-up shoe.
Two embodiments of the segmented die are disclosed. In both embodiments, the segments have a semi-circular shaped pipe-contacting surface. In one embodiment, each segment has a semi-circular shaped outer edge. In another embodiment, each segment has an outer edge formed of a flat top portion and two angled portions forming lateral extensions, which extend outwardly from the opening of each semi-circle. These lateral extensions provide a die with exterior dimensions that fit within a pipe-bending machine over a range of different pipe diameters. Both embodiments permit flexibility in die construction. In other applications, the pipe-bending surfaces may be concave or convex and the placement of the segments may be offset axially or laterally to produce different shapes in the pipes being bent.
A principal object and advantage of the invention is the provision of a segmented pipe-bending die.
Another object and advantage of the invention is the provision of a segmented pipe-bending die, which has no moving parts.
Still another object and advantage of the invention is the provision of a segmented pipe-bending die that is formed of segments each having a semi-circular pipe-contacting surface.
A still further object and advantage of the invention is the provision of a segmented pipe-bending die where each semi-circular segmented has a radius of different length.
Another object and advantage of the invention is the provision of a segmented pipe-bending die that may be more easily fabricated and at lower cost than forged steel molded dies.
The above objects are realized with a segmented pipe bending die comprised of a plurality of segments each having a semi-circular pipe contacting portion with adjacent segments having different length radii to produce a curved pipe contacting surface along all the segments forming the die.
The foregoing, as well as further objects and advantages of the invention will become apparent to those skilled in the art from a review of the following detailed description of my invention, reference being made to the accompanying drawings.